Really strange knock from the rear


4Motion, baby!
2007 Golf V
I have a really strange, intermittent knocking noise coming from the rear of my car. Sometimes I hear it going over bumps or seams on the rod, and sometimes when coasting to a stop. Sometimes even when pulling away and letting go of the gas. It's not a clunking noise but rather sounds like a tap on a plastic piece with a hammer. Not very loud either.

I checked the underside real quick when I had my tires changed and didn't find anything loose. I've also checked that it's not something / someone (!) in my trunk.

My car is a 4Motion so could it be a CV joint going bad in the rear? The boots seemed OK when I checked them and I don't hear a constant knocking like you normally hear from a bad CV joint when driving in a tight circle. Perhaps a sway bar link? I even checked the drive shaft links for play but they seemed OK.

Has anyone experienced anything similar?